On Dec 3, 2009, at 9:25 AM, Ralph Parker wrote:
> For all you young whipper-snappers with two letter calls who don't believe it:
> 9 Mc. SSB mixed +/- with a 5 Mc. VFO did indeed result in opposite sidebands.
> I was there.
No a 9 MHz IF will not swap sidebands. But, as N1AL has mentioned, a 5 MHz IF with 9 MHz VFO will swap sidebands.
I didn't want to clutter the reflector since I thought Al has settled it, but to put another nail in the coffin, here was my email to Al last night:
> You are right of course, Al.
>
> In the 9 MHz IF case, a superhet gives f(IF) = f(RF) + f(LO) for both 20m and 80m. It is the sign of f(LO) that changes with the band.
>
> Thus, df(IF)/df(RF) = 1 for both 20m and 80m.
>
> In the 5 MHz IF case, it is f(IF) = f(RF) - f(LO) for 20m, but it is f(IF) = f(LO) - f(RF) for 80m. df(IF)/df(RF) = 1 for 20, but it is -1 for 80m.
the df(IF)/df(RF) are just partial derivatives. If the value is +1, USB in RF results in USB in IF. If it is -1, USB in RF results in LSB in IF.
73,
Chen, W7AY
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